diff --git a/types/file-size/file-size-tests.ts b/types/file-size/file-size-tests.ts
new file mode 100644
index 0000000000..ea8a804070
--- /dev/null
+++ b/types/file-size/file-size-tests.ts
@@ -0,0 +1,10 @@
+import fileSize = require("file-size");
+
+const fz = fileSize(14235235);
+
+fz.fixed; // $ExpectType number
+fz.spacer; // $ExpectType string
+
+fz.human(); // $ExpectType string
+fz.calculate(); // $ExpectType Calculated
+fz.to("KB"); // $ExpectType string
diff --git a/types/file-size/index.d.ts b/types/file-size/index.d.ts
new file mode 100644
index 0000000000..72359e1bb5
--- /dev/null
+++ b/types/file-size/index.d.ts
@@ -0,0 +1,39 @@
+// Type definitions for file-size 1.0
+// Project: https://github.com/Nijikokun/file-size
+// Definitions by: Richie Bendall <https://github.com/Richienb>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 3.5
+
+interface Options {
+    fixed?: number;
+    spacer?: string;
+}
+
+type Spec = "si" | "iec" | "jedec";
+
+type Unit = "B" | "KB" | "MB" | "GB" | "TB" | "PB" | "EB" | "ZB" | "YB";
+
+interface Bits {
+    result: number;
+    fixed: string;
+}
+
+interface Calculated {
+    suffix: string;
+    magnitude: number;
+    result: number;
+    fixed: string;
+    bits: Bits;
+}
+
+interface Result {
+    human(spec?: Spec): string;
+    to(unit: Unit, spec?: Spec): string;
+    calculate(spec?: Spec): Calculated;
+}
+
+declare function fileSize<T extends Options>(bytes: number, options?: T): Required<T> & Result;
+
+export as namespace filesize;
+
+export = fileSize;
diff --git a/types/file-size/tsconfig.json b/types/file-size/tsconfig.json
new file mode 100644
index 0000000000..0fcc7d5f02
--- /dev/null
+++ b/types/file-size/tsconfig.json
@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictFunctionTypes": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "file-size-tests.ts"
+    ]
+}
diff --git a/types/file-size/tslint.json b/types/file-size/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/file-size/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }